Titanium oxide particles and method of producing same

ABSTRACT

Titanium oxide particles comprising particulate titanium oxide substrate having a zinc oxy compound or a combination of a zinc oxy compound and a silicon oxy compound supported thereon. They can be produced by adding a zinc compound or a combination of a zinc compound and a silicon compound together with an alkali to a dispersion of particulate titanium oxide substrate to neutralize the zinc compound or the combination of the zinc compound and the silicon compound in said dispersion, then separating and drying the resultant product. They are useful for pigments, catalysts, catalyst supports and adsorbents, and particularly excellent in deodorizing performance by removing malodorous gases such as ammonia, methyl mercaptan, hydrogen sulfide, trimethylamine, methyl sulfide and acetaldehyde through decomposition and adsorption thereof, so that they are useful as white deodorants for sanitary objects such as paper diaper and sanitary napkins which come to directly contact with the skins of human beings.

This is a continuation-in-part application of U.S. application Ser. No.08/069,416 filed on Jun. 1, 1993 now U.S. Pat. No. 5,480,636, alldisclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to titanium oxide particles useful forpigments, catalysts, catalyst supports, adsorbents and the like, andmore particularly, to titanium oxide particles having a high specificsurface area useful for deodorants adsorbing obnoxious gases such asammonia, mercaptans, hydrogen sulfide and aldehydes as well as forscavengers capable of removing noxious materials by decomposing themthrough photocatalytic reaction.

2. Description of Related Art

Obnoxious gases widely produced in inhabitant environments includeammonia, methyl mercaptan, hydrogen sulfide, trimethylamine, methylsulfide, and acetaldehyde. An attempt has been made to remove theseobnoxious gases allowing maintenance of pleasant inhabitantenvironments, for example, techniques of removing odor by adsorbingobnoxious gases on activated carbon or impregnated activated carboncontaining acids or alkalis have been employed. However, these activatedcarbons are black and so limitted in their application. For example,when the activated carbons are incorporated in sanitary products such aspaper diapers and sanitary napkins which come into direct contact withthe skins of human beings, such treatments as not rendering the productsblack in color to have a clean feel to the products are required, orwhen the activated carbons are to be incorporated in interior wallsheets, decorations and cosmetics, the products are difficult to imparta desired color so that they are applied to only black products.Moreover, there are problems that the activated carbons has specificallya low ability in deodorization of ammonia and a reduced performance inremoving obnoxious gases if they adsorb first moisture.

On the other hand, there have been marketed a variety of adsobents, forexample, white ones capable of imparting a clean feel to the products aswell as coloring them in desired tinge such as silica gel, zeolite,activated alumina and activated terra abla. However, these whiteadsorbents have a low deodorizability to the aforementioned obnoxiousgases so that they can not be substituted for activated carbons.

As one of the white deodorants, there have been proposed particleshaving a firmly bonded structure produced with zinc oxide, titaniumdioxide and water as disclosed in Japanese Patent Publication(Post-Exam.) No. Hei 3-33022.

According to the disclosure of this Patent, the white deodorants can beproduced by preparing a mixed aqueous solution of a water solubletitanium compound and a soluble zinc compound and an alkaline aqueoussolution, and combining both the solutions to achieve a pH in the rangeof 6 to 11 of the mixed solution, thereby effecting neutralization toproduce a precipitate comprising zinc oxide, titanium dioxide and water,from which solid particles having a firmly bonded structure of a uniformcomposition are subsequently formed. In this method, the concentrationsof the starting materials such as a titanium compound and the like andthe velocity of combining both the solutions must be preciselycontrolled rendering the operation complicated. In addition, when the pHof the combined solution shifts to outside the defined range, theresultant white deodorant has poor characteristics as disclosed inJapanese Patent Publication (Post-Exam.) No. Hei 3-33022. Moreover, theprecipitate produced by the neutralization is in a gel state which tendsto be difficult to flitrate, and when dried, the particles of theprecipitate may coagulate so firmly that it is difficult to pulverize.Thus, there remain many things to be improved.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a process forproducing conveniently and easily white particles having an excellentdeodorizing performance by removing malodorous gases throughdecomposition and adsorption thereof.

It is another object of the present invention to provide titanium oxideparticles comprising particulate titanium oxide substrate having anamount of a zinc oxy compound supported thereon in a molar ratio of thetotal Ti amount included in the substrate to the Zn amount of said zincoxy compound, i.e., Ti:Zn=9.9:0.1 to 5:5, said zinc oxy compound beingproduced by neutralizing a zinc compound with a water soluble compoundof alkali metal or alkaline earth metal.

It is still another object of the present invention to provide titaniumoxide particles comprising particulate titanium oxide substrate having azinc oxy compound and a silicon oxy compound supported thereon in amolar ratio of the total Ti amount included in the substrate to the Znamount of said zinc oxy compound, i.e., Ti:Zn=9.9:0.1 to 5:5, and in amolar ratio of the Zn amount of said zinc compound to the Si amount ofsaid silicon oxy compound, i.e., Zn:Si=9:1 to 0.1:9.9, respectively.

It is still another object of the present invention to provide a processfor producing titanium oxide particles comprising particulate titaniumoxide substrate having a zinc oxy compound supported thereon, comprisingadding a water soluble compound of alkali metal or alkaline earth metaland a zinc compound to a dispersion of the substrate to neutralize thezinc compound in said dispersion, then separating and drying theresultant product.

It is still another object of the present invention to provide a processfor producing titanium oxide particles comprising particulate titaniumoxide substrate having a zinc oxy compound and a silicon oxy compoundsupported thereon, comprising adding a zinc compound and a siliconcompound and a neutralizing agent to a dispersion of the substrate toneutralize the zinc compound and the silicon compound in saiddispersion, then separating and drying the resultant product.

It is still another object of the present invention to provide titaniumoxide particles useful as a deodorant or a noxious material scavenger.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the experimental results in photocatalyticdecomposition of acetaldehyde.

FIG. 2 is a graph showing the experimental results in photocatalyticdecomposition of methyl mercaptan.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present inventors have made an intensive research to render titaniumoxide more valuable as functional material, during which an interest hasbeen directed to application of titanium oxide to white deodorant. As aresult of the proceeded research, it was found that titanium oxide isexcellent in performance of removing basic gases such as ammonia andtrimethylamine, but poor in removing obnoxious gases such as methylmercaptan and hydrogen sulfide. After the further strenuous research hasbeen made, it has been found as a result that titanium oxide particlesobtained by supporting on particulate titanium oxide substrate the zincoxy compound which has been produced by neutralizing a zinc compoundwith a water soluble compound of alkali metals and alkaline earth metalsare (1) excellent in the deodorizing performance in removing obnoxiousgases, (2) producible through filtration, drying and milling of theproduct which are easily performed without requiring any complicatedoperation, and (3) reproducible easily with consistent quality suitablein practical use. The present invention takes into consideration suchfindings.

In our subsequent research, it was found that when the aforementionedtitanium oxide particles supporting zinc oxy compound are used asdeodorant in paper diaper, the zinc oxy compound supported on theparticulate titanium oxide substrate is dissolved in urine, whichresults in a reduced deodorizing performance in removing methylmercaptan, hydrogen sulfide and the like, or which the dissolved zincions have a possibility of adversely affecting human beings. Then afurther research has been made to overcome the difficulties, and as aresult, we have found that if a silicon oxy compound is added to thetitanium oxide particles supporting zinc oxy compound, less amount ofzinc oxy compound is dissolved and the particles have a high deodorizingperformance by removing obnoxious gases, on the basis of which thepresent invention is derived.

In our additionally subsequent research, it was found that the titaniumoxide particles supporting zinc oxy compound, or those supporting inaddition silicon oxy compound are capable of removing deleteriousmaterials such as malodorous gases, irritating materials, materialsadversely affecting human beings and environment through decompositionthereof by photocatalytic reactions upon irradiation with lightincluding ultraviolet radiation in the presence of oxygen, especiallycapable of effecting deodorization by removing the malodorous gasesthrough decomposition thereof. The present invention has beenaccomplished based on the aforementioned findings.

The present invention is concerned with titanium oxide particlescomprising particulate titanium oxide substrate having a specific amountof a zinc oxy compound supported thereon, or those having specificamounts of zinc oxy compound and a silicon oxy compound supportedthereon. As used herein, the term "titanium oxide" refers also tohydrated titanium oxide besides so-called titanium oxide. The term "zincoxy compound" refers to zinc oxide and zinc hydroxide. The term "siliconoxy compound" refers to silicon oxide, silicic acid and silicates. Asused herein, the term "supported" refers to any condition where the oxycompounds are supported on the substrate, for example, where the zincoxy compound, silicon oxy compound, or the like are locally or uniformlypresent on the surfaces of a single substrate particle or a coagulate ofsubstrate particles, or where they are coated in a continuous coating onthe surfaces of substrate particles, or where they are taken into theinterstices in the substrate particles, so long as the zinc oxycompound, silicon oxy compound and the like are physically or chemicallyin contact with substrate particles. The amount of the zinc oxy compoundto be supported on the particulate titanium oxide substrate may varydepending upon the composition of malodorous gases in consideration. Ingeneral, it should be in a molar ratio of the total Ti amount includedin the substrate to the Zn amount of the zinc oxy compound, i.e.,Ti:Zn=9.9:0.1 to 5:5, more desirably 9.5:0.5 to 7:3. If the amount ofthe zinc oxy compound to be supported is lower than the defined range,the end product will have undesirably a reduced deodorizing performancein removing methyl mercaptan and hydrogen sulfide. If it is larger thanthe defined range, the end product will have undesirably a reduceddeodorizing performance in removing ammonia and trimethylamine, or anincreased amount of free zinc oxide or hydroxide.

The present invention is the titanium oxide particles comprisingparticulate titanium oxide substrate having the zinc oxy compound andthe silicon oxy compound supported thereon where the amount of thesilicon oxy compound to be supported may vary depending upon thecomposition of malodorous gases in consideration. In general, the amountof the zinc oxy compound to be supported should be in a molar ratio ofthe total Ti amount included in the substrate to the Zn amount of thezinc oxy compound, i.e., Ti:Zn=9.9:0.1 to 5:5, more desirably 9.5:0.5 to7:3, and the amount of the silicon oxy compound to be supported shouldbe in a molar ratio of the Zn amount of the zinc oxy compound to the Siamount of the silicon oxy compound, i.e., Zn:Si=9:1 to 0.1:9.9, moredesirably 9:1 to 4:6. If the amount of the silicon oxy compound to besupported is lower than the defined range, the zinc oxy compound will beliable to dissolve in an aqueous solution, particularly an acidicsolution and when used as the deodorant in paper diaper, may undesirablycause a reduction in deodorizing performance or a fear of adverselyaffecting human beings with the dissolved zinc ions. If the amount ofthe silicon oxy compound to be supported is larger than the definedrange, the end product will have undesirably a reduced deodorizingperformance in removing specific malodorous gases though less amount ofthe zinc oxy compound is dissolved.

When the titanium oxide particles are used especially as deodorant, theyshould have a specific surface area of 100 m² /g or more to achieve agood deodorizing speed and higher deodorizing performance. A specificsurface area lower than 100 m² /g results in an substantiallyinsufficient deodorizing performance making it difficult to obtain gooddeodorants.

According to the process of the present invention, the titanium oxideparticles comprising particulate titanium oxide substrate having a zincoxy compound supported thereon is produced by adding a zinc compound andan alkali to a dispersion of the particulate titanium oxide substrate,to neutralize the zinc compound in said dispersion, then separating anddrying the product.

The particulate titanium oxide substrates to be used in the presentinvention include those obtained by various known methods. As processesfor production of particulate titanium oxide substrates, there are, forexample, 1 a process of hydrolyzing a titanium compound such as titanylsulfate, titanium chloride and an organic titanium compound under heat,if necessary, in the presence of seed for nucleation, 2 a process ofneutralizing a titanium compound such as titanyl sulfate, titaniumchloride and an organic titanium compound by adding an alkali thereto, 3a process of oxidizing titanium chloride, an organic titanium compoundand the like in a vapor phase, and 4 a process of calcining the titaniumoxide obtained in the aforementioned processes 1, or 2 at a temperatureof about 600° C. or less.

In the process of the present invention, the particulate titanium oxidesubstrate is dispersed in a solvent such as water, and if necessary,classified, to produce a dispersion. To the dispersion, there is added azinc compound which may be any one of various zinc compounds such aszinc chloride, zinc sulfate, zinc nitrate and the like. The alkalis tobe used include desirably water soluble compounds of alkali metals andalkaline earth metals such as sodium hydroxide, potassium hydroxide,sodium carbonate, sodium bicarbonate, sodium silicate, and bariumhydroxide. The use of ammonia or ammonium salts as alkalis isundesirable, because they have a tendency to form complex ions with thezinc compounds causing dissolution of zinc oxide. The neutralization ofthe zinc compounds in the dispersion of the particulate titanium oxidesubstrate may be performed by any one of procedures of, for example,adding simultaneously the zinc compound and the alkali to saiddispersion, or adding the zinc compound to said dispersion and thenadding the alkali, or adding the alkali to said dispersion and thenadding the zinc compound. The zinc oxy compound is generallyprecipitated by conducting neutralization at a pH in the range of 6 to11. The conditions of the concentration of the particulate titaniumoxide substrate in the dispersion, the amount of the zinc compounds orthe alkalis to be added, the concentration of each of them when used asan aqueous solution, the speed of addition, and the temperature at theneutralization reaction are not critical, but can optionally be set.Prior to the neutralization reaction, any one of dispersants such asorthophosphoric acid, pyrophosphoric acid, hexametaphosphoric acid,alkali salts thereof, sodium orthosilicate, and sodium metasilicate maybe added to the dispersion, provided that the deodorizing performance ofthe titanium oxide particles is not adversely affected, in order toimprove the distribution of the particulate titanium oxide substrate inthe dispersion thereof.

The product produced in this way is separated and, if necessary, washed,and then dried. The separation may be effected by normal filtration ordecantaion. The drying may be effected at a temperature of 100° to 600°C., preferably 100° to 200° C. The dried product may be disintegrated orground to produce powders, or shaped into granules for the end uses.

An increased amount of the zinc oxy compound supported on theparticulate titanium oxide substrate tends to reduce the specificsurface area of the titanium oxide particles. It is desired, therefore,to employ such particulate titanium oxide substrate as having a specificsurface area of larger than 100 m² /g in order to produce titanium oxideparticles having a specific surface area of larger than 100 m² /g.

In the process of the present invention, the titanium oxide particlescomprising particulate titanium oxide substrate having zinc oxy compoundand a silicon oxy compound supported thereon can be produced inaccordance with the process as described above for making zinc oxycompound supported on the particulate titanium oxide substrate. That is,a zinc compound, a silicon compound and a neutralizing agent are addedto the dispersion of particulate titanium oxide substrate to neutralizethe zinc compound and the silicon compound in the dispersion to producea product which is separated and dried. The silicon compounds to be usedinclude various silicon compounds such as water-glass, sodiumorthosilicate, sodium metasilicate, and silicon chloride. Theneutralizing agents include various acids such as hydrochloric acid,sulfuric acid, and nitric acid. The neutralization of the siliconcompounds may be effected according to the neutralization process asdescribed above for the neutralization of the zinc compounds, generallyat a pH in the range of about 6 to 11 to produce a precipitate. The zinccompounds and the silicon compounds may be simultaneously neutralized,or alternatively, separately neutralized. The simultaneousneutralization results in coprecipitation of a zinc oxy compound and asilicon oxy compound which are supported on the particulate titaniumoxide substrate. In effecting separately each neutralization, forexample, the zinc oxy compound is supported on the particulate titaniumoxide substrate, followed by making the silicon oxy compound supportedthereon. When the titanium oxide particles according to the presentinvention are used as deodorant, one of the most preferred process forthe production thereof is to neutralize or hydrolyze a titanium compoundwith an alkali to produce particulate titanium oxide substrate in theliquid phase, followed by adding simultaneously a zinc compound, asilicon compound and a neutralizing agent to the liquid dispersion ofthe particulate titanium oxide substrate to produce the titanium oxideparticles having a zinc oxy compound and a silicon oxy compoundsupported thereon.

The conditions of the concentration of the particulate titanium oxidesubstrate in the dispersion, the amounts of the silicon compounds, thezinc compounds and the alkalis to be added, the concentration of each ofthem when used as an aqueous solution, the speed of addition, and thetemperature at the neutralization reaction are not critical, but canoptionally be selected.

The product produced in this way is separated and, if necessary, washed,and then dried in accordance with the identical procedure to thatdescribed above for supporting the zinc oxy compound. The separation maybe effected by normal filtration or decantation. The drying may beeffected at a temperature of 100° to 600° C., preferably 100° to 200° C.The dried product may be disintegrated or ground to produce powders, orshaped into granules for the end uses.

According to the present invention the titanium oxide particlescomprising the particulate titanium oxide substrate having a zinc oxycompound supported thereon or the titanium oxide particles comprisingthe particulate titanium oxide substrate having a zinc oxy compound anda silicon oxy compound may be used alone as deodorant or as noxiousmaterial scavenger, or alternatively, may be used in combination withordinary materials which have been used in the art such as aluminumoxide, zeolite and the like.

Various malodorous gases can effectively be removed by contacting themwith the deodorants of the present invention. In addition, variousdeleterious materials can effectively be converted into non-deleteriousmaterials by contacting them with the scavengers of the presentinvention under irradiation of light including ultraviolet radiation inthe presence of oxygen. The ultraviolet radiations to be used in thepresent invention are preferably near ultraviolet radiations having awavelength in the range of 300 to 400 nm. The deleterious materialscavengers of the present invention can apply to a wide variety ofobnoxious materials such as malodorous materials, irritating materials,and other materials which adversely affect human beings and their lifeenvironment. Examplary functions of the scavengers are decomposition ofthe aforementioned malodorous gases and air-polluting gases such asnitrogen oxides, sulfur oxides, and water-polluting materials such asoils, and other organic compounds such as polybiphenyl chloride anddioxine as well as sterilization.

When the titanium oxide particles of the present invention are used as anoxious material scavenger or deodorant capable of decomposing noxiousmaterials by a photocatalytic reaction, the particles should preferablyhave a specific surface area of 100 m² /g or more, more preferably 150m² /g or more, most preferably 200 m² /g or more. If the specificsurface area is less than 100 m² /g, then the photocatalytic reaction iseffected with a reduced efficiency, so that they cannot appropriately beused as the noxious material scavenger or deodorant.

Moreover, the titanium oxide particles comprising particulate titaniumoxide substrate having a zinc oxy compound are useful for pigments,catalysts, catalyst supports, adsorbents and the like. Particularly,they are excellent in deodorizing performance by removing malodorousgases such as ammonia, methyl mercaptan, hydrogen sulfide,trimethylamine, methyl sulfide, acetaldehyde and the like throughdecomposition thereof and useful for white deodorants capable ofdeodorizing sanitary objects such as paper diaper and sanitary napkinswhich are directly in contact with skins of human beings.

Furthermore, the titanium oxide particles can effectively and promptlyremove deleterious materials by photocatalytic reactions so that theyare quite useful as deodorants not only for industrial use but also forordinary domestic use. The noxious material scavengers of the presentinvention find application to a wide variety of deleterious materialsand are highly safe to be disposable without polluting the environmentso that they are very useful in industry.

The process of the present invention can conveniently and easily producestable quality titanium oxide particles and is extremely useful inindustry in that the product is relatively rapidly filtrable andwashable during the production thereof and the particulate mass producedafter drying can be easily disintegrated and readily pulverized.

The present invention will be described with reference to some Examplesand Comparative Examples together with accompanying drawings.

EXAMPLE 1

Ten liters of a 2 mol/l solution of titanyl sulfate were hydrolyzedunder heat in the presence of seeds for nucleation to produce aprecipitate. The precipitate was subsequently flitrated, washed, anddried to produce particulate titanium oxide substrate which had aspecific surface area of 290 m² /g as determined by the B.E.T. method(as used hereinunder).

Then 80 grams of the particulate titanium oxide substrate were dispersedin one liter of pure water, and heated to a temperature of 40° C.,followed by the dropwise addition of a 2N aqueous solution of sodiumhydroxide to control the pH of the dispersion at 8. Then with stirring,to the dispersion there were added dropwise simultaneously 110 ml of a 1mol/l aqueous solution of zinc chloride and a 2N aqueous solution ofsodium hydroxide over 10 minutes while maintaining the pH of thedispersion at 8 to yield a product. Subsequently the product wasfiltered, washed, dried at a temperature of 120° C., and thendisintegrated to yield titanium oxide. particles according to thepresent invention (Sample A).

EXAMPLE 2

The same procedure as in Example 1 was repeated, except that 50 ml ofthe aqueous solution of zinc chloride were added dropwise, to yieldtitanium oxide particles of the present invention (Sample B).

EXAMPLE 3

The same procedure as in Example 1 was repeated, except that 430 ml ofthe aqueous solution of zinc chloride were added dropwise, to yieldtitanium oxide particles of the present invention (Sample C).

EXAMPLE 4

80 grams of the particulate titanium oxide substrate produced accordingto the process as described in Example 1 were dispersed in one liter ofpure water. To the dispersion was added 15 grams of powdery zincchloride, followed by heating to a temperature of 40° C. Then, to thedispersion with stirring there were added dropwise a 2N aqueous solutionof sodium hydroxide over 10 minutes to control the pH of the dispersionat 8 to produce a product. Subsequently the product was filtered,washed, dried at a temperature of 120° C., and then disintegrated toyield titanium oxide particles according to the present invention(Sample D).

EXAMPLE 5

80 grams of the particulate titanium oxide substrate produced accordingto the process as described in Example 1 were dispersed in one liter ofpure water. To the dispersion was added 8.9 grams of sodium hydroxide,followed by heating to a temperature of 40° C. Then, to the dispersionwith stirring there were added dropwise 110 ml of a 1 mol/l aqueoussolution of zinc chloride over 10 minutes to control eventually the pHof the dispersion at 8 to produce a product. Subsequently the productwas filtered, washed, dried at a temperature of 120° C., and thendisintegrated to yield titanium oxide particles according to the presentinvention (Sample E).

EXAMPLE 6

One liter of a 1 mol/l aqueous solution titanium tetrachloride washydrolyzed under heat in the presence of seeds for nucleation to producea titanium oxide precipitate. (The titanium oxide precipitate afterfiltered, washed and dried had a specific surface area 160 m² /g.)

After the thus produced dispersion of particulate titanium oxidesubstrate was conditioned to a temperature of 40° C., to the dispersionwas added dropwise a 2N aqueous solution of sodium hydroxide to controlthe pH of the dispersion at 8. Then with stirring, to the dispersionthere were added dropwise simultaneously 110 ml of a 1 mol/l aqueoussolution of zinc chloride and a 2N aqueous solution of sodium hydroxideover 10 minutes while maintaining the pH of the dispersion at 8 to yielda product. The product was filtered, washed, dried at a temperature of120° C., and then disintegrated to yield titanium oxide particlesaccording to the present invention (Sample F).

COMPARATIVE EXAMPLE 1

One liter of a 1 mol/l aqueous solution of zinc chloride was heated to atemperature of 40° C., to which solution with stirring, was addeddropwise a 2N aqueous solution of sodium hydroxide over 100 minutes tocontrol the pH of the aqueous solution at 8 to yield a product. Theproduct was filtered, washed, dried at a temperature of 120° C., andthen disintegrated to yield zinc hydroxide particles (Sample G).

COMPARATIVE EXAMPLE 2

The titanium oxide produced by the process in Example 1 withouteffecting any other treatment was used as Sample H.

In all the Examples 1 to 6, the filtration and washing of theprecipitates could be relatively rapidly achieved and the powderyproducts after drying were easily disintegrated and easily pulverized.

The specific surface areas and the adsorption rates of the Samples A toH obtained in Examples and Comparative Examples are reported in Table 1.

The following procedure was used to evaluate the Samples for theadsorption of malodorous gases: First each of trimethylamine, methylmercaptan and hydrogen sulfide were diluted with nitrogen gas to about1000 ppm. Then one liter of the diluted gas was introduced into apolyester bag containing 0.1 gram of the Sample and after sealed, leftto stand for 5 hours. Thereafter, the concentration of the malodorousgases remaining in the bag was measured by a gas chromatography or a gassensor and the adsorption rates were calculated from the concentrationvalues of the diluted gases introduced.

                                      TABLE 1                                     __________________________________________________________________________                                 Percent gas adsorption (%)                                  Molar ratio                                                                         Color of                                                                           Surface area   Methyl                                                                              Hydrogen                                  Sample                                                                            Ti:Zn particles                                                                          (m.sup.2 /g)                                                                         Trimethylamine                                                                        mercaptan                                                                           sulfide                            __________________________________________________________________________    Example 1                                                                            A   9:1   White                                                                              235    63.4    99.7  100                                Example 2                                                                            B   9.5:0.5                                                                             White                                                                              242    73.4    91.8  100                                Example 3                                                                            C   7:3   White                                                                              174    57.2    99.3  100                                Example 4                                                                            D   9:1   White                                                                              237    61.6    99.5  100                                Example 5                                                                            E   9:1   White                                                                              228    60.4    98.8  100                                Example 6                                                                            F   9:1   White                                                                              144    42.9    65.8  100                                Comparative                                                                          G    0:10 White                                                                               26    16.6    35.7  100                                Example 1                                                                     Comparative                                                                          H   10:0  White                                                                              290    60.0    10.7  10.0                               Example 2                                                                     __________________________________________________________________________

EXAMPLE 7

150 ml of a 1 mol/l aqueous solution of titanium tetrachloride wereheated to a temperature of 40° C., to which solution with stirring a 4Naqueous solution of sodium hydroxide was added dropwise over 10 minutesto control the pH of the aqueous solution at 3 to produce a titaniumoxide precipitate.

To the dispersion of particulate titanium oxide substrate with stirring,there were added dropwise simultaneously 50 ml of a 3 mol/l aqueoussolution of zinc chloride, 36.8 grams of sodium orthosilicate and a 4Naqueous solution of sodium hydroxide over 10 minutes while maintainingthe pH of the dispersion at 8 to yield a product. The product wasfiltered, washed, dried at a temperature of 120° C., and thendisintegrated to yield titanium oxide particles according to the presentinvention (Sample I).

EXAMPLE 8

The identical procedure to that in Example 7 was repeated, except that225 ml of the aqueous solution of titanium tetrachloride, 75 ml of theaqueous solution of zinc chloride and 9.2 grams of sodium orthosilicate,to yield titanium oxide particles of the present invention (Sample J).

EXAMPLE 9

The identical procedure to that in Example 7 was repeated, except thatno sodium orthosilicate was added, to yield titanium oxide particles ofthe present invention (Sample K).

The specific surface areas and the adsorption rates of the Samples I toK obtained in Examples were measured and the results are set forth inTable 2. It can be found that the Samples are excellent in adsorptionrate with malodorous gases and preferred as white deodorants.

Next, one gram of each of the Samples was dispersed in 100 ml of a 0.01Naqueous solution of hydrochloric acid and 100 ml of a 0.01N aqueoussolution of sodium hydroxide, respectively, agitated for 3 hours at atemperature of 40° C., and then the supernatant was removed to evaluatethe amount of zinc ions present therein by an emission spectroscopy. Theresults are shown in Table 3. It can be seen that Samples I and J aresoluble in an alkaline aqueous solution to almost the same extent, butless soluble in an acidic aqueous solution as compared with Sample K.

                                      TABLE 2                                     __________________________________________________________________________                                Percent gas adsorption (%)                                  Molar ratio                                                                         Color of                                                                           Surface area   Methyl                                                                              Hydrogen                            Sample    Ti:Zn:Si                                                                            particles                                                                          (m.sup.2 /g)                                                                         Trimethylamine                                                                        mercaptan                                                                           sulfide                             __________________________________________________________________________    Example 7                                                                           I   3:3:4 White                                                                              297    56.1    89.6  100                                 Example 8                                                                           J   4.5:4.5:1                                                                           White                                                                              299    64.4    99.3  100                                 Example 9                                                                           K   5:5:0 White                                                                              206    62.6    99.1  100                                 __________________________________________________________________________

                  TABLE 3                                                         ______________________________________                                                   Concentration of zinc ions                                                    (expressed by ZnO) (mg/l)                                                       Aqueous hydrochloric                                                                         Aqueous sodium                                           Sample                                                                              acid solution  hydroxide solution                                ______________________________________                                        Example 7                                                                              I       200            1 or less                                     Example 8                                                                              J       280            1 or less                                     Example 9                                                                              K       400            1 or less                                     ______________________________________                                    

COMPARATIVE EXAMPLE 3

A mixed solution of 100 ml of a 1 mol/l aqueous solution of zincchloride and 900 ml of a 1 mol/l aqueous solution of titaniumtetrachloride was heated to a temperature of 40° C., to which solutionwith stirring a 4N aqueous solution of sodium hydroxide was addeddropwise at a rate of 10 ml/min. to control the pH of the mixed solutionat 8 to yield a product. The product was filtered, washed, dried at atemperature of 120° C., and then disintegrated to yield particles oftitanium oxide and zinc hydroxide (Sample L).

The Samples A and L obtained in Example and Comparative Example wereevaluated for ability of photocatalytically decomposing malodorousgases.

First, 0.1 gram of each of the Samples was dispersed in 5 ml of ethanoland the dispersion was poured into a schale of a diameter of 8.6 cm anddried at a temperature of 70° C. to be deposited uniformly on the bottomsurface of the schale. These schales were placed in a closed plasticvessel having a inner volume of about 8 liters equipped with 4 W blacklight, into which acetaldehyde and methyl mercaptan were injected,respectively. Then after leaving to stand for 2 hours under dark, theblack light was turned on to effect a photocatalytic reaction and thevariation in the concentration of malodorous gases in the inside of theclosed vessel was determined by a gas chromatography. The irradiationintensity of the light having a wavelength in the range of 310 to 400 nmwas about 1 mW/cm².

The photocatalytic decomposition of acetaldehyde is shown in FIG. 1 andthat of methyl mercaptan in FIG. 2. The kinetics of the photocatalyticreaction with the black light being turned on were determined from theslope of the linear portion of the curves shown in FIGS. 1 and 2, theresults of which are indicated in Table 4.

                  TABLE 4                                                         ______________________________________                                                     Rate constant (min.sup.-1)                                              Sample  Acetaldehyde                                                                             Methyl mercaptan                                    ______________________________________                                        Example 1                                                                              A         4.7 × 10.sup.-3                                                                    1.2 × 10.sup.-2                           Comparative                                                                            L         1.0 × 10.sup.-3                                                                    7.2 × 10.sup.-3                           Example 3                                                                     ______________________________________                                    

What is claimed is:
 1. A method of scavenging a noxious material whichcomprises,applying to noxious materials in need of scavenging, ascavengingly effective amount of a noxious material scavenger, anddecomposing the noxious materials by a photocatalytic reaction, saidscavenger comprising: particulate titanium oxide substrate having a zincoxy compound supported thereon in a molar ratio of the total Ti amountincluded in the substrate to the Zn amount of the zinc oxy compound,i.e., Ti:Zn=9.9:0.1 to 5:5, said zinc oxy compound being produced byneutralizing a zinc compound with a water soluble compound of alkalimetal or alkaline earth metal, said particulate titanium oxide substratehaving a specific surface area of 100 m² /g or more, wherein saidscavenger decomposes noxious materials by a photocatalytic reaction. 2.A method of decomposing malodorous gases which comprises,applying to themalodorous gases an amount of a deodorant effective to decompose themalodorous gases, and decomposing the malodorous gases by aphotocatalytic reaction, said deodorant comprising:particulate titaniumoxide substrate having a zinc oxy compound supported thereon in a molarratio of the total Ti amount included in the substrate to the Zn amountof the zinc oxy compound, i.e., Ti:Zn=9.9:0.1 to 5:5, said zinc oxycompound being produced by neutralizinq a zinc compound with a watersoluble compound of alkali metal or alkaline earth metal, saidparticulate titanium oxide substrate having a specific surface area of100 m² /g or more, wherein said deodorant decomposes malodorous gases bya photocatalytic reaction.